Process for treating brush bristles



Jan. 25, 1955 s. DREYFUS 2,700,259

PROCESS FOR TREATING BRUSH BRISTLES Filed Sept. 15, 1950 2 Sheets-Sheet l 1N VEN TOR.

5 Vain Dra fix; BY

ATTom/EY Unite States Patent C) PRQCESS FOR TREATING BRUSH? BRISTLES Sylvain Dreyfus, Lausanne, Switzerland Application September 15, 1950, Serial No. 185,002

iaims priority, application- Switzerland October 10, 1949 1 Claim. (Cl; 51-281) This invention. relates to the manufacture of brushes, more particularly toothbrushes, and is especially concerned with a machine for finishing the ends of thev bristles of brushes.

In the manufacture of brushes, such as tooth brushes, it is necessary to blunt the free ends of the bristles because these ends, when merely cut, are sharp and would, if not blunted, injure the mouth and gums of the users.

It is the principal object of the presnt' invention to provide a device for effectively and efficiently blunting the ends of the bristles of tooth brushes and the like.

It is another object of the invention to provide a device of the character indicated which is adapted to blunt the ends of the bristles in such manner that the lateral surfaces of the bristles are connected to. the top surfaces of the bristles, i. e. the free ends of the bristles, by sloping surfaces which form at all; points an. obtuse angle with the lateral surfaces and with the top surfaces.

Another object of the invention is to provide a device for blunting the free ends of the bristles of a tooth brush or the like which provides on the bristles a sloping surface with a convex curvatureconnectingthelateral surface and the top surface of each bristle.

The above and other objects and features of the invention will be more readily apparent from the following detailed description thereof when read in connection with the accompanying drawings. It will: be understood;,however, that the drawings are directed solely to illustrative embodiments of the invention and are notlimitative of the invention, the scope of the invention being defined in" the appended claim.

In the drawings, wherein like reference characters designate like parts,

Fig. l is a top plan view of a device embodying features of the invention, the upper' brush holding member being removed to show details of construction;

Fig. 2 is a side elevation, partly in section, of the embodiment shown in Fig. 1, showing the upper brush holding member in position;

Fig. 3 is a plan view of a modified form of the brush holding member;

Fig. 4 is a front elevation, partly in section taken approximately along the line IVIV of Fig. 3, showing the brush holding member mounted in position;

Fig. 5 is a side elevation, in greatly enlarged scale, of a brush bristle blunted by the device of the invention;

Fig. 6 is a diagrammatic plan view of another embodiment of the invention; and

Fig. 7 is a similar view of a further embodiment of the invention.

The bristle blunting machine of the invention comprises at least one support means, means for securing at least one brush on the support means, a second support means adapted to hold a sheet of material having at least one abrasive face, a frame, at least one rotatable shaft mounted on the frame, a crank pin eccentrically supported by the shaft, and at least one member movable in a plane perpendicular to said shaft and crank pin and connected to said crank pin, one of said above-mentioned supports being rigidly connected to said movable member, while the other of said supports is positioned adjacent the support connected to the movable member in such manner that the ends of the bristles of the brush held in the first support touches the abrasive face of the sheet held by the other support.

In Figures 2 to 4 there is shown a support 5' or 5a upon which are mounted a plurality of tooth brushes 4. A rigid platform 6 carries a sheet of emery paper or emery cloth 7, the abrasive surface 7a of which is turned upwards. The platform 6 provides a connecting element between two rotatably mounted parallel: axles B, B which are positioned' to rotate about two parallel axles A, A. The axles'A, A thus define twocranks having the same radius, as shown inFig. 2.

On a frame plate 8- aremountedthe two axles- A, A having bases 13 and 13' and pins 13a on which shafts 9 and 9 are rotatably mounted. The axles A, A have threaded ends 13b which are securely screwed in plate 8. The rotatable shafts 9 and 9' carry pulleys 10 and 10. The pulley 10' is. double and has two parallel grooves around one of which passes a belt 11 connecting the pulley 10 to the pulley 10 on shaft 9, and the other groove of. the pulley 10 carries a belt 12 connecting the pulley 10' to the power source, such as a. motor (not shown). The axles B and B are formed by two bases 15 and 15' similar in construction. to bases 13 and 13' and secured firmly into platform 6 and rotatably mounted in hollow shafts 14 and 14' which are fastened to pulleys 10 and 10. As shown-in Fig. 2, the groove of pulley 10' and the groove of pulley 10' which carries the belt 11 are of equal diameters so that the belt 1 1 merely serves to insure that the dead-point: of the cranks willbepassed at all times. By reference to the drawings it will be seen that, when the pulleys 10 and 10 are rotated, allpointsof the abrasive surface 7a are moved along identical circumferences, the radii of which correspond to the distance between the'axles A and B. Thus, referring to Fig. 1, if the bristles of a tooth brush 4 were. mounted to: engage the abrasive surface 7'a, each bristle of the end tuft of brush 4-Would slide along a circumference C1. A bristle of the end tuft of the brush at the left in Fig. 1 would be rubbed along a circumference C2, whereas the rearward bristles of the brushes 4- would' be moved along one of the circumference (:3. In the foregoing, itwill be understood that the support 5 holding. thebrushes 4 is stationary and disposed in such manner that the ends of the bristles touch the abrasive surface 7a.

In Fig. 3 is shown a brushsupport 5a comprising at least two sections to permit one of the sections to be filled with brushes while the other holds the brushes in active position against the abrasive surface 7a. Support 5a is in the form of a rectangular frame, the sides 18 of which are suificiently long topermit two rows of brushes to be placed therein, the brushes in the-rows being parallel to the sides 18 and in head abutting; relationship. The frame is. provided with a rigid; base 26. upon which the heads of the brushes press. The handles of the brushes engage blocks 34 so that the bristles are maintained in the proper position relative to the surface 7a. As shown in Fig. 3, the heads of the brushes are directed toward the center of the frame. The brushes of each row are pressed against the rigid base 26 by a resilient blade 16 which normally has a convex cross-section but which,

however, is flattened when the blade 16 is passed through apertures 17 in portions 18a of the edges 18 of the frame. The inner portions of the edges 18 are of lesser width to avoid contact with the platform 6. The apertures 17 are positioned at the level of the brush handles or slightly lower and are of a sufficient height to receive the blades 16.

The end walls of the frame, which are designated 19, are perpendicular to the plane in which the brushes lie and are provided with external cars 20, 20' having apertures in which are received cylindrical sleeves 21, 21 perpendicular to the rigid base 26. These sleeves are slidably adjustable on cylindrical stems 22, 22 which are fixedly mounted in the plate 8 parallel to the axles A and B.

Springs 23 are mounted on the stems 22, 22 and exert an upward pressure upon the frame to maintain it in raised position on the stems. The upper ends of the stems 22, 22 are threaded as indicated at 25 and are engaged by nuts 24 which permit the frame to be moved downwardly against the force of the springs 23 to adjust the distance between the brush bristles and the abrasive surface 7a and thereby to adjust the degree of flexing imparted to the bristles 3 as they are pressed against the abrasive surface. The direction of flexing of the bristles when the platform is moved in the direction of the arrow 1 is shown in Fig. 4.

It will be understood that the sliding of the bristles over the abrasive surface due to the relative motion of the two supports 5a and 6 (Figs. 3 and 4) is not exactly the same as the relative circular motion of the supports. Owing to the fact that this latter motion is changed at each instant, the angle at which each filament is flexed turns about an axis which is perpendicular to the surface 7a While the end of each bristle describes, relatively to the surface 7a, a circumference which by reason of the flexion between the bristles and the surface 7a is smaller than the circumference C1, C2. The flexion causes a delay in the rotation of the angle of flexing and this efiect is greater, the greater the coeflicient of friction between the abrasive surface and the bristle. Thus, the sliding of the bristle ends could be substantially annulled if the radius of the cranks were not greater than the length of the normal projection of the flexed bristle on the surface 70:. For this reason and in order to increase the speed of the abrasive action with a reasonable angular speed of the cranks, the radius of the cranks is a matter of a few centimeters when the device is adapted for the processing of tooth brushes. Because the ends of the bristles must be blunted along their entire periphery, the greatest radius that can be given to the cranks isthat in which the abrasive action is suflicient after a single rotation, increased by the value of the angle of friction the tangent of which is equal to the coetficient of friction between the bristles and the abrasive surface.

In using the device one may start by first giving the bristles their greatest flexion and then gradually diminishing it by turning the nuts 24 to allow the support 26 to be raised by the springs 23, or one may proceed in the opposite manner by gradually increasing the flexion of the bristles.

The embodiments of Figs. 6 and 7 permit substantially the same results to be obtained as are obtainable in the embodiments of Figs. 1 to 4. In Fig. 6 there is obtained a relative movement of the two supports which is as close as desired to the circumference C1, C2 of Fig. 1 by means of a single crank. A platform 6a having a stem 27 forms a connecting rod articulated at B, the axis of the crank pin turning around the axis A and the platform is guided by its stem 27 at a distance several times greater than the crank radius, the stem 27 extending between two fixed pins 28. This connecting rod may carry either the abrasive material or the brush support and these are carried nearer the axis B than to the portion of the stem 27 extending between the pins 28, in order that the movement path of the moving surface relative to a fixed point will be as near as possible to a circle for a given distance between the pins 28 and the axis A.

In Fig. 7 a connecting rod 29 is articulated at one end about an axis B of a crank pin turning about an axis A and at its other end to sliding block 30 carried in a rectangular slideway 31. The connecting rod imparts an alternating motion to the block 30 which may, for example, be transferred to the abrasive surface. The sliding block forms an integral part of the platform or support 6b.

As in the case of Fig. 4, one can impart to the brush, by movement of the shaft 33, a slow small vertical motion in order to shape the filaments as rounded off points rather than cones. The breadth of the platform 6 is not limited provided the pins 13a and 15 are long enough to avoid a seesawing action caused by the pressure of the brushes.

The device could be adapted for blunting the bristles of brushes other than tooth brushes, e. g. hand brushes, and the device is particularly suitable for treatment of nylon bristles. Finally, the desired relative movement of the surfaces could be obtained by other forms of the embodiments illustrated, using one or several cranks.

What I claim is:

A process for blunting and rounding the ends of brush bristles having the bristle ends lying in a common plane which comprises, bringing the brush bristle ends into engagement with an abrasive surface, effecting relative movement between the abrasive surface and the brush bristle ends in a transverse and in a longitudinal direction to cause each brush bristle end to describe a predetermined closed path, the path described by each bristle being eccentric with respect to the path described by each other bristle, pressing the brush bristles against the abrasive surface to cause the brush bristle ends to be flexibly bent during said relative movement, and gradually relieving the pressure of the bristle ends upon the abrasive surface while continuously effecting said relative movement, whereby to effect controlled rounding of the bristle ends to provide a convex sloped surface connecting the end of the bristle with the lateral surface of the bristle.

References Cited in the file of this patent UNITED STATES PATENTS 74,560 Maury Feb. 18, 1868 122,951 Mallon Jan. 23, 1872 1,495,747 Izawa May 27, 1924 1,551,659 Gouldbourn Sept. 1, 1925 1,705,767 Izawa Mar. 19, 1929 1,888,675 Izawa Nov. 22, 1932 2,159,336 Markwick et al May 23, 1939 2,227,126 Cooke Dec. 31, 1940 2,365,396 Cunningham Dec. 19, 1944 2,412,141 Ford Dec. 3, 1946 FOREIGN PATENTS 3,698 Great Britain Feb. 20, 1893 9,233 Great Britain May 2, 1905 

